Elevator gate



H. ISAACS ELEVATOR GATE Feb. 21, 1967 2 Sheets-Sheet l Filed Nov. 18, 1964 INVENTOR. HAROLD ISAACS BY (W ATTORNEY Feb. 21, 1967 H. lsAAcs 3,305,111

ELEVATOR GATE Filed Nov. 18, 1964 l 2 Sheets-Sheet 2.

40 INVENTOR.

HAROL D ISAACS BY n. i f

ATTORN E Y United States Patent 3,305,111 ELEVATOR GATE Harold Isaacs, University Heights, Ohio, assigner to Techno Products, Inc., a corporation of Ohio Filed Nov. 18, 1964, Ser. No. 412,212 1 Claim. (Cl. 214-77) This invention relates generally to an elevator gate for trucks and more particularly to an improved mechanism for raising and lowering an enlarged elevator gate platform.

Existing elevator gates are characterized by their very limited capacity to accommodate loads of eit-her a very heavy or a bulky nature. This weight and space limitation penalizes the loading and unloading eiiiciency in that existing industrial trucks and similar material-handling equipment or systems for loading and unloading trucks cannot be fully utilized. Consequently, the application of a unit load system as characterized by pallets, containers, platform trucks or similar means is not generally feasible. More specifically, presently goods cannot be loaded and unloaded together with hand trucks or other industrial truck devices, because normally they cannot be transferred from the pavement, ground, or floor to the platform surface and raised with the platform by the lifting mechanism.

While these shortcomings have been recognized for some time, no simple solution has as yet been found. Trhe problems are numerous. As alluded to above, one difficutly arises from the fact that the conventional loadbearing sur-face of the platform is too far removed from the ground. This condition exists because the upper as well as the lower link of the parallelogram lifting systern is directly secured to the platform. Therefore it is necessary to make the platform relatively high. Necessarily the links are spaced fairly close together. It is obvious that the closeness of the lifting links places extremely high stresses upon the lifting system making it impractical to raise substantial loads whose center of gravity is a great distance from the forward edge of the platform. The entire load is cantilevered from the forward edge of the platform.

The vertical spacing between the links cannot be arbitrarily increased. The platform surface must of course have a low platform height to permit loading and unloading. The difficulty with the height of the platform is not readily solved by a ramp, as it is almost always necessary that the ramp be of a rather short and steep incline construction. This in turn makes it impossible for an average man to pull a unitized heavy load upon the platform with manually propelled industrial trucks. The gradients of such ramps are usually in excess of 25%. Indeed manually as well as power propelled industrial trucks do not have suticient ground clearance to negotiate much more than a gradient.

It is therefore the primary object of this invention to provide an elevator gate which is adapted to overcome the above mentioned diiiiculties.

It is a further and more particular object of this invention to provide an elevator gate having the capability of lifting a loaded, propelled, industrial truck and accommodating the transfer of such truck from the ground over the platform to the truck bed.

It is still a further object of this invention to provide an elevator gate having a lifting mechanism which includes a vertical link spacing the links of the parallelogram lifting system to facilitate and permit the accomplishment of the foregoing objectives.

It is a still further object of this invention to provide an elevator gate in which the lifting mechanism is secured to the platform in a manner to permit the loadbearing sur-face ,thereof to be at least 50% closer to the ground than conventional elevator gate platforms of the type here under consideration.

It is a still further object of this invention to provide an elevator gate in which the ramp leading to the platform has a `gradient permitting the use of industrial truck equipment.

An aspect of the present invention resides in the provision of an elevator gate `for a truck which has a suitable arrangement to mount the gate. The gate includes a load-bearing platform with a width approximating that of the truck. A parallelogram linkage system is provided, including a lifting link located at each side of the platform, the linking system extends substantially parallel to the longitudinal axis of the truck. The platform is also provided with support pivot points located proximate to the end face of eac'h side and the axis across these pivots constitutes the pivotal axis about which relative rotation between the linkage system and the platform takes place. One end of the lifting link is lmounted to and about the pivot point. The parallelogram linkage system also includes a tension link which is arranged parallel to the lifting link and in spaced relation to the platform. A structural member is provided for suitably connecting the tension and the lifting link. 'Ihe links are angularly moved about the folding axis by a mechanism, suitably arranged and secured to the truck, to elevate and to lower the plat-form.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and their scope will be pointed out in lthe appended claims.

In the drawings:

FIGURE l is a plan view of an elevator .gate in accordance with this invention and an illustration in `outline form of various parts of the truck to which the elevator gate is secured;

FIGURE 2 is a perspective view, partly fragmentary, of the elevator gate shown in FIGURE 1 in accordance with this invention;

FIGURE 3 is an enlarged side view of the parallelogram linkage mechanism;

FIGURE 4 is an enlarged elevational view in section taken along line 4 4 of the elevator gate shown in FIG- URE l.

Referring now to the drawings, there is shown in FIGS. 1 and 2 an elevator gate 10 in a lowered position and adapted to be used in conjunction with and secured to a partly shown truck which, for ease of describing this invention, includes a truck bed 12 and two-longitudinally extending frame members 14.

The elevator gate 10 comprises a load-bearing platform 16 having a transverse dimension approximating the width of the truck bed 12.

The platform is constructed of a frame 16a and a plurality of longitudinally extending I beams (not shown) etxending therebetween. Suitable wooden planks 16h are neatly fitting between the faces of the I beams.

The platform 16 is raised and lowered in a horizontal plane relative to the truck bed 12 and supported in elevated and lowered position by a parallelogram linkage lifting system 18 situated on each side of the platform 16. The linkage system 18, see FIG. 3, includes a tension link 24 and a parallel disposed and vertically spaced lifting link 20 rotatably mounted about a pivot pin 22 located near and mounted on the end face of the platform proximate to the forward end thereof. 'Ilhe pivot pin 22 on each side of the platform establishes the pivotal axis about which the lifting link moves angularly relative to the platform 16 and the axis about which the latter can be folded to a vertical plane. Folding can be accomplished manually or by means of a power operated device which does not form part of this invention.

The tension link 24 is not directly secured to the platform 16. A vertically extending connecting link 26 is pivotably mounted at one end about pivot pin 22 and the other end is constructed to pivo-tably receive and secure about pivot pin 28 one end of the tension link 24. This avoids the requirement of vertically spacing the pivot axes of links 20 and 24 directly on the platform itself and permits a much lower height of the platform than otherwise possible. A suspension member 30, for instance in the form of a chain or rod, extends diagonally from the -vertical link 26 rearward to the rear portion of the platform 1:6 land is at both ends pivotably mounted. The `suspension member 30 maintains the platform 16 in a normally horizontal plane and permits the same to be folded vertically whenever such condition is desirable.

The forward end of the linkage mechanism 18 includes a second Vertical connecting link 32 which is adapted to receive or support about vertically spaced and suitably mounted pivot pins 34 land 36 the lifting and tension link 24 and 20, respectively. Tht pivot pin 36 is mounted to constitute an integral part of a torque tube 38 hereafter further described.

Rigidly secured to and transversely disposed between each parallelogram linkage system 18 and more particularly the lifting links 20 thereof, is the torque tube 38 which serves to equalize the mechanical and hydraulic load upon each linkage mechanism. As shown in Elf"- URE 4, the lifting link 2t) is welded, or alternatively otherwise secured, to the torque tube 38 while the vertically extending link 32 is mounted about the integral pin 36 of the tube 38 to permit relative rotary motion between the two members. The link members 20, 24, 26 and 32 thus form in effect a parallelogram linkage system for raising and lowering the platform 16 in a horizontal plane.

The vertical link 32 attaches directly and indirectly to a plurality of cross members 40 by means of a transversely extending bar 32a, and in particular to cross carrier member 40a, see FIG. 4. A plurality of structural members I4017 are spacedly disposed transverse between the cross members 40 and welded or otherwise secured thereto to establish rigidity and structural strengths in the suspending and supporting network. The cross members 40 which are rigidly bolted, at 41, to the frame member 14 'of the truck as is shown in FIGURES 1 and 2, to suspend and support the entire above described elevator gate unit.

Pivotably anchored to and provided between the forward end of the lifting link 20 and carrier member 40' is a hydraulically actuated cylinder and piston 44 as shown in FIGURE 3. The piston V44 is structurally offset relative to the link 20 land connected thereto by bolt 4411. Fluid under pressure is supplied to the hydraulic member 44 from a pump and tank 46. One hydraulic power source can serve each linkage system 18 and piston pertaining thereto on both sides of the platform 16.

Adjacent the platform 16 a ramp 50 is hingedly connected thereto. The ramp can be folded over for storing purposes. Preferably, the ramp 50 is folded in a clockwise direction. The ramp is supported on the ground by a plurality of angle irons 56 welded to the bottom of the ramp 50. The heights of these irons 56 diminishes toward the rear, see FIG. 2, withsa resultant ramp gradient of less than 10%. The length of each angle iron approximates the width of the I beam (not shown) web to fit between the flanges of each I beam of the platform 16. The height of the largest angle iron 56 does not, or not substantially, exceed the depth -of the web so that the ramp can be folded substantially flush with the platform 16. A spring biased member l52 extending from platform 16 serves to maintain the ramp approximately horizontal while the platform is in a lowered or raised position. A Very similarly functioning member 54 mounted on link 26 serves to releasably engage the socket 55 on platform 16 to maintain the platform in folded or vertical position.

In operation, the structural members 4t), 46a, 41, 32

and 32a remain rigid and stationary. In response to a demand signal, a pump, not shown, causes fluid from the tank 46 to flow into cylinder 44 to move the piston therein to increase the distance between the anchoring points 44a and 44h, see FIG. 3, and to angularly move the lifting link 2l) relative to the platform. By angularly moving the link 2%, the forward end of the platform is raised horizontally together with the 4vertical connecting link 26. The suspension member 30, by virtue of its connection to and between link 26 and the far end of platform 16, maintains the platform 16 in a horizontal plane.

The link 24, connected between the station-ary vertical link 32 and lthe moving link 26, remains under tension at all times during the upward position of the platform and establishes the parallel and vertical position of link 26.

As the angularity between the horizontal links and 24 relative to the vertical links 26 and 32 changes, the pla-tform is raised or lowered.

While there have been described what are at present considered to be the preferred embodiments of this in- Vention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claim to cover all such changes and modications as fall within the true spirit and scope of the invention.

What is claimed is:

An elevator gate for a truck having suitable supporting means therefor, comprising in combination: a load bearing platform approximating the width of the truck provided with transversely spaced, longitudinal extending, supporting structures; a parallelogram linkage system located on each side of said platform and forward end portions thereof being adapted for connection with the support means 'of the truck; said system including a lifting link, a tension link disposed in parallel and in vertically spaced relation to said lifting link and to said platform, and a vertical link effective for connecting said aforesaid links; an elongated torque member disposed transversely between and rigidly secured to the forward end of the lifting links and movably connected to the lower end of each vertical link, said member being effective for equalizing the lifting action between said lifting links; the upper end of said vertical link being adapted for rotatably receiving the forward end of the tension link and being rigidly connected to the supporting means of the truck; hydraulic actuator means vertically interposed between said lifting links and the support means of the truck for angularly moving the lifting links relative to said vertical links to elevate and lower the platform; and a ramp hingedly secured to the rearward end of said 55 platform and extending therefrom at a gradient less than 10%, said ramp being provided with a plurality of sectional angle irons located perpendicular to the supporting structures of said platform, the heights of said irons diminishing from the forward end toward the rear and each section `of the angle iron being adapted for fitting between said supporting structures for establishing a substantially flush surface `with said platform when the ramp is in folded position.

References Cited by thek Examiner UNITED STATES PATENTS FOREIGN PATENTS 6/ 1935 Germany.

GERALD M. FORLENZA, Primary Examiner.

R. G. SHERIDAN, Assistant Examiner. 

